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I would really appreciate some opinions on the following models, as well as suggestions on better alternatives in the $1000 vicinity:

1. Casio CDP-220R2. Yamaha DGX-640(and perhaps not the same kind of "machine" at all, but with a lot of good functions, such as audio recording from mic-in):3. Casio WK-7500

Sound and "Build" quality... and opinions about useful built-in functions.

Would you have to buy external speakers to get a good sound from any one of them?

Are most of the sounds drums and "unnecessary" things in the ones with extremely many sounds, so that a few good sounds would be better?

It should be as an alternative to play, instead of the real piano, so it shouldn't be just a digital piano with one or a few good piano sounds, nevertheless it would be great with a really nice "grand piano" sound.

If you're gigging regularly with it, or you have roadies tossing it into and out of trucks, build quality is more of an issue than if you're setting it up in a room in the house and leaving it there, just playing it without it getting knocked around. Drums sounds are useful to some people and completely unnecessary to others. Some external speakers will be worse than built-ins, some will be better, but it will be dictated somewhat by your budget and by how loud you want to play (and to some extent also by placement issues).

It sounds like you want a decent piano sound, but its piano functionality is second to its ability to provide you with other capabilities, yes? Then getting an idea of what other functionalities you're looking for would be important.

Anyway, of the models you mention, the CDP-200 appears to be pretty rare in the U,S,, I've never seen one or talked to anyone who has one. The DGX-640 has better quality sounds overall than the WK-7500 (at least in my opinion), but each has some capabilities the other lacks... and there is a big difference between the feel of their actions. I think the WK-7500 has an above average feeling keyboard for an unweighted model, but if you're looking for something with any sense of the key-weightedness of a piano, the DGX has it, the WK does not. OTOH, while the WK action may not feel as good for piano playing, it will probably feel better for organ playing, for example. (And it has a nice "drawbar organ" functionality uilt into it, one of its features that the DGX lacks.)

Hopefully that at least gives you a few angles to consider that may help. But if you want someone's suggestion of "best keyboard under $1k," the answer really varies depending on "for what."

You might want to consider the Kurzweil SP4-7. I paid well under $1k for a B-stock unit. The action is good enough (just) for reasonably expressive piano playing. The EPs are pretty darn good, and the organ is one of the best in a non-clonewheel board (particularly if you load OS2 and install the additional PC3 patches available from Kurzweil). On top of that are some very good synth and orchestral sounds. Drum kits are included, but you'd need to drive them from an external sequencer (IIRC).

The acoustic pianos on the SP4 series will not compete with the latest from Yamaha, Roland, Nord and Kawai, but for occasional use, they're OK.

The unit is very solidly constructed (much more robust than the other boards you mention in your original post).

_________________________"you don't need to have been a rabbit in order to become a veterinarian"

I haven't heard or seen a Casio CDP 200. I assume this model replaces the CDP 100 which is a popular entry level model that has been around for some time. I think the CDP-100 is now discontinued. The DGX 640 and the WK-7500 both have good sounding acoustic pianos. Many of the other sounds are good as well, however this is somewhat subjective. The action is different between these three with the WK having a non weighted keyboard.

The WK also has many other features the DGX 640 does not have like the ability to create and edit sounds, rhythms, and pattern sequencing--building a song measure by measure. There are some you tube videos that show how to do this. These are advanced capabilities. There is also on on-board sequencer to record with and you can plug in a mic and another instrument directly into the WK. So to sum up it depends on what you want to do, what kind of action you want, and whether you need a piano or a workstation.